[en] The motional behaviour of hexadecane-h₃₄ within the pseudo-hexagonal channels provided by the urea-d₄ framework has been studied by incoherent quasielastic scattering between 5 K and 370 K. On the instrument time scale (80 μeV), at least two components could be separated, which are attributed to reorientational jumps of the paraffins around their long axes and damped librations, respectively. At 147 K a phase transition takes place involving an orthorhombic deformation of the host channels and a simultaneous change of 60 degrees to 180 degrees jumps. From the activation energy it is concluded that the motional properties of the included molecules are responsible for this transition. (author) 6 refs., 4 figs